This 5.1 MHz circuit was found in a 1980s documentation. The frequency is given by the crystal and general purpose transistors can be used.
This 1968 documentation circuit uses a relay to control loads up to 1 kW (depends on relay...
We found this conventional receiver circuit in a 1990 documentation. The circuit includes an audio...
This circuit for the positive front of a rectangular signal was found in an old documentation, but applies...